The present invention relates in general to medical devices and more particularly to a combined tissue/bone growth stimulator and external fixation device.
External fixation devices are often used in the treatment of fractures, soft tissue injuries and reconstructive surgery. External stabilization devices or splints are frequently used to position a fracture or osteotomy in proper alignment during the healing process. External fixation devices may also be used in a variety of clinical procedures to lengthen or shorten bone, or to delay joint replacement. Multiple bone screws are often used to provide interfragmental compression or to attach plates which provide compression, prevent displacement of bone or tissue fragments and support the fractured bone or tissue fragments during healing. These screws, wires and/or pins are placed through one or both cortices of bone to properly position and align the fracture, non-union or osteotomy. Delayed union or non-union bone fractures are typically considered injuries that have not made satisfactory progress towards healing. External fixation devices allow easy access to wounds, adjustment during the course of healing and often allow more functional use of the fractured limb. Such devices may be used in place of a conventional cast.
For example, some conventional fixation devices may be used to adjustably secure a first bone portion above an osteotomy in a position relative to a second bone portion below the osteotomy. Unfortunately, many of these devices may impair a physician""s ability to monitor the healing process and/or access the area surrounding the osteotomy. For example, some conventional fixation devices may block or limit examination techniques such as radiographic, ultrasonic and/or visual examination of a treatment site.
Pulsed electromagnetic field (PEMF) therapy has been used to treat therapeutically resistant problems of the musculoskeletal system. Examples of PEMF therapy include treatment of non-union bone fractures and delayed union bone fractures. PEMF therapy has also been used for treatment of various types of soft body tissue injuries.
PEMF therapy has been satisfactorily used in treating spinal fusion, failed arthrodeses, osteonecrosis, and chronic refractory tendinitis, decubitus ulcers and ligament, tendon injuries, osteoporosis, and Charcot foot. During PEMF therapy, an electromagnetic transducer coil is generally placed in the vicinity of the musculoskeletal injury or body tissue injury (sometimes referred to as the xe2x80x9ctarget areaxe2x80x9d or xe2x80x9cselected portionxe2x80x9d) such that pulsing the transducer coil will produce an applied or driving field that penetrates to the underlying damaged bone or other body tissue. PEMF therapy typically uses low-energy, timevarying electromagnetic fields.
However, the healing process may still require an extended time, even with the use of external fixation devices. Complications may sometimes occur from the use of external fixation devices in such procedures. Complications such as infection at the pin or screw interface with a patient, may result in pin loosening and lessen the effectiveness of the external fixation device.
In accordance with teachings of the present invention, disadvantages and problems associated with the use of external fixation devices have been substantially reduced or eliminated.
One aspect of the present invention is a combined tissue/bone growth stimulator and external fixation device to aid in the treatment of fractures, osteotomies, soft tissue injuries, and reconstructive surgery and to reduce the likelihood of complications. The tissue/bone growth stimulator apparatus includes an external fixation device for stabilization of a selected portion of a patient. The tissue/bone growth stimulator apparatus also includes an electrical circuit attached to and forming an integral component of the external fixation device and operable to generate an electrical drive signal. The tissue/bone growth stimulator apparatus also includes a cable adapted to connect the electrical drive signal to a stimulator portion operable to provide an electromagnetic field to stimulate the growth of bone and tissue at the selected portion of the patient and/or at other portions of the patent. More particularly, the electromagnetic field may be produced by directing a current through the external fixation device into the patient.
The external fixation device can interface with the patient using stabilization devices such as pins, bone screws, or wires which are implanted in the patient according to known methods. The external fixation device can act to stabilize, compress, or distend the selected portion of the patient. For example, the external fixation device can compress a bone fracture, aiding the treatment by increasing the contact area of the fracture and decreasing the fracture gap. The external fixation device may be selectively adjusted in length or position to aid in effective treatment. In one embodiment the length of the external fixation device can be selectively lengthened or compressed. For example, the frame fixation device may be gradually shortened to compress a fracture or gradually lengthened to aid in limb lengthening or contraction.
Another aspect of the present invention includes providing an electrical circuit that generates a pulsed current that may travel through two or more pins and which provides an electromagnetic field to the target area of the patient held by the external fixation device. Another aspect of the present invention includes providing at least one electromagnetic transducer coil fixed to the external fixation device to provide an electromagnetic field to the targeted portion of the patient. According to another embodiment of the present invention the electromagnetic coil may be selectively positioned to provide PEMF therapy to the target area of the patient. For example, the electromagnetic coil may be located to provide PEMF therapy to a fracture or to an area of tissue damage. Treating the target area of the patient with the electromagnetic field may increase bone mineral density and stimulate tissue growth. Such an advantage may decrease the time needed for healing.
According to another embodiment of the invention, the apparatus is operable to reduce the likelihood of infection at the patient interface. The device achieves the advantages of using a traditional external fixation device but with a lower risk of complication from infection. For example, the patient interface may be susceptible to osteomylitis or other infections which the present invention may prevent or cure. A further advantage is that the fixation of the electromagnetic transducer coil ensures that the targeted area will routinely receive the desired PEMF treatment.
Additionally, in the event the patient either develops or has a pre-existing infection at or around the patient interface, the tissue/bone growth stimulator may aid in recovery from the infection. Additional technical benefits include increasing the effectiveness of the external fixation device by reducing the risk of pin loosening caused by infection.
Another advantage of the present invention is that therapy may be initiated by a physician and may continue to operate for a predetermined treatment cycle such as four hours per day until removal of the fixation device or change in treatment cycle. As a result further patient or physician intervention may not be required to ensure completion of a treatment cycle once initiated.